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Web Server Extensions
mod_jk, also known as Apache Tomcat Connector, is an Apache HTTP Server module that enables communication between Apache HTTP Server and Apache Tomcat, a web server and servlet container for Java applications.

Here are the key aspects and features of mod_jk:

Integration between Apache and Tomcat: mod_jk acts as a bridge between the Apache HTTP Server and Apache Tomcat, allowing them to work together seamlessly. It facilitates the forwarding of requests from Apache to Tomcat for processing Java-based applications.

Load Balancing: mod_jk supports load balancing capabilities, enabling the distribution of incoming requests across multiple Tomcat instances. It implements algorithms like round-robin, weighted, or session-based load balancing to distribute the workload efficiently.

Request Routing: mod_jk provides request routing functionality, allowing Apache to route specific URLs or URL patterns to the corresponding Tomcat instances based on configurable rules. This helps in directing requests to specific applications or servlets running on Tomcat.

Failover and High Availability: In case a Tomcat instance becomes unavailable or fails, mod_jk can automatically redirect requests to a backup Tomcat instance, ensuring high availability of the applications. Failover and session replication mechanisms are supported for maintaining session state across instances.

SSL/TLS Support: mod_jk supports secure connections through SSL/TLS protocols. It can handle secure communication between the client and Apache HTTP Server, as well as between Apache and Tomcat, ensuring the encryption of sensitive data.

Connection Pooling: mod_jk incorporates connection pooling capabilities, optimizing the utilization of backend connections between Apache and Tomcat. This can help in reducing the overhead of establishing new connections for each request, improving overall performance.

Logging and Monitoring: mod_jk provides logging capabilities, allowing administrators to monitor and track requests, errors, and performance metrics between Apache and Tomcat. This aids in troubleshooting and performance analysis.

mod_jk is a widely used module for integrating Apache HTTP Server with Apache Tomcat, enabling the deployment of Java applications within a scalable and flexible architecture. It offers features like load balancing, failover support, request routing, and secure communication, enhancing the performance, availability, and security of Java-based web applications.